Patent GB-371856-A (GB)
Title: Improvements in electric switchgear
IPC: H01H71/52
Filed: 1931-01-22
Abstract: 371,856. Automatic circuit-breakers; controllers. COX, F. B., 65, Fleet Street, Liverpool. Jan. 22, 1931, No. 2133. [Classes 38 (iii) and 38 (v).] In electric switchgear a handle when moved away from its "on" position closes one switch and then when returned to its " on " position closes another switch, and if subsequently moved slightly away from its " on " position it operates a safety device which causes the first switch to open before the second. The switchgear is shown in Fig. 4 as applied to starting a motor M through a resistance K but can also be applied to star-delta and autotransformer starters. The handle H when moved from the " on " position, shown dotted, to the position shown in full lines, closes a switch A on to contacts C and also a switch B on to contacts S thus completing the starting connection. The handle also moves a percussive member W adjacent to a no-volt magnet N, the percussive member being latched in that position by a detent T. Movement of the handle H to the "on" position releases a detent Q from the catch B which thereupon springs towards and closes running contacts R. The handle H in this position also releases the detect T from the percussive member W so that upon de-energization of the magnet N, the member W will fall upon the switch A and knock it to the open position. During movement of the handle H towards its " on " position, its tail h<1> moves upwards the end e<2> of a lever E, but this movement has no effect on a safetv device F. However, any movement of the handle H from its "on" position, causes downward movement of the end e<2> with consequent movement of the device F and opening of contacts D, causing de-energization of the magnet N and release of the percussive member W to engage and open the switch A. An overload coil O may also cause opening of contacts D. In one modification, Fig. 3 (not shown), the switch A is spring biased to its open position and is retained closed by a detent released upon de-energization of the no-volt magnet, a percussive member not being used. This modification is further modified, Fig. 2 (not shown), in that the handle H itself functions as the switch B, but there are no starting contacts, only running contacts corresponding to the contacts R. The device F and switch A can be combined as shown in Fig. 2A. Slight movement of the handle H from the full line position, or overload in the coil O, causes the detent E to release the spring opened switch Af. Thereafter further movement of the handle H away from its " on " position recloses the switch Af, and movement of the handle H to its " on " position completes the circuit at contacts C<1>. In another modification, Fig. 1 (not shown), the switch A is replaced by an electromagnetic contactor which is energized when the contacts D are closed. Movement of the handle from its "off" position prepares a starting circuit and closes the contacts D against an opening spring, the contacts D being latched closed. Movement of the handle to its " on " position closes running contacts and movement away from the " on " position releases the latch on contacts D, which thereupon open and de-energize the contactor. Specifications 234,171, 249,232, 262,488, 262,698, 264,552, 278,119, [all in Class 38 (iii), Electric motor control systems &c.], and 348,590 are referred to.